1. Field of the Invention
The present invention relates to magnetoresistive films for use in reproduce magnetic heads, magnetic sensors or the like.
2. Description of Related Art
A magnetoresistive (MR) element is an element which detects an intensity of magnetic field and its changes by supplying a current to a magnetoresistive film and reading the voltage changes thereacross. An MR head employing such a magnetoresistive element offers a higher detectivity relative to conventional inductive heads, and accordingly increased investigations upon the MR head have been directed to its applications to reproduce magnetic heads such as hard disk drives which demand higher density recording. In order for such a MR head to be feasible in achieving high density recording, it must have a high magnetic field sensitivity As a result, a significant need has arisen for a MR element which exhibits a high MR ratio. A giant magnetoresistive (GMR) element is known as exhibiting such a high MR ratio. Examples of magnetic films for such a GMR element include artificial lattice type magnetic films having ferromagnetic layers alternating with nonmagnetic conductive layers, spin valve type magnetic films having a layered structure consisting of antiferromagnetic/ferromagnetic/nonmagnetic conductive/ferromagnetic layers, coercive force differential type magnetic films having a multilayer structure consisting of ferromagnetic/nonmagnetic conductive/ferromagnetic layers with the ferromagnetic layers having coercive forces different from each other.
A magnetic film for the GMR elements has been proposed by M. Jimbo et al.(J. Appl. Phys., 79 (1966) 6237-6239) which employs an amorphous ferromagnetic layer for the ferromagnetic layer and has a multilayer structure of NiO/a-CoFeB/Cu/a-CoFeB.
However, the MR films employing such an amorphous ferromagnetic layer suffer poor reproducibility in their formation to disadvantageously exhibit varied qualities from film to film. In addition, they exhibit a lower MR ratio than MR films employing a crystalline ferromagnetic layer.